Transcriptome sequencing and simple sequence repeat marker development for three Macaronesian endemic plant species1

The availability of next-generation sequencing (NGS) technology for nonmodel organisms in prime ecological scenarios has revolutionized evolutionary biology (Egan et al., 2012). An exciting prospect of NGS is the potential to improve our understanding of the genetic basis of processes such as adaptation and speciation (Stapley et al. Volcanic oceanic islands have long served as model systems for the study of such evolutionary processes (Emerson, 2002); however, the capabilities of NGS for oceanic island en-demics are only starting to be realized (Kueffer et al., 2014). For example, NGS approaches have been employed to investigate the radiation of Darwin's finches from the Galápagos Islands (Lamichhaney et al., 2015) and to untangle the complex phylo-genetic relationships of Tolpis Adans., a genus of flowering plants from Macaronesia (Mort et al., 2015). NGS has also been successfully applied to other " island-like " scenarios such as the radiation of cichlid fishes in African and Neotropical lakes (Fan et al., 2012). While NGS is becoming more affordable, the cost of obtaining genome-level sequences from multiple individuals or population sampling is still high. However, a large genetic resource from just a single or a few individuals (e.g., a transcriptome sequence or an expressed sequence tag [EST] library) offers the ability to produce highly cost-effective PCR-based molecular markers that can be amplified in many individuals at a fraction of the cost (Ellis and Burke, 2007). To generate further interest in this area and to develop a novel genetic resource, we have sequenced and assembled transcriptome sequences for three plant species (Argyranthemum broussonetii (Pers.) Humphries [Asteraceae], Descurainia bourgaeana (E. Fourn.) Webb ex O. E. Schulz [Brassicaceae], and Echium wildpretii H. Pearson ex Hook. f. [Boraginaceae]) that belong to three endemic radiations of Macaronesia (Fig. 1). Isolated oceanic archipelagos are botanically diverse and rich in endemic species, making them ideal systems to investigate the origin and evolution of plant diversity (Losos and Ricklefs, 2009; Kueffer et al., 2014). These taxa have been selected because they belong to genera that offer exceptional " natural laboratories " in the Macaronesian archipelagos with which to investigate a range of evolutionary phenomena., including a rare putative example of homoploid hybrid speciation (Brochmann et al., 2000; Fjellheim et al., 2009). There are seven species of Descurainia Webb & Berthel. endemic to the Canary Islands where they exhibit multiple independent adaptations to high-altitude habitats 1 Manuscript • Premise of the study: Oceanic islands offer unparalleled …